The proposed research examines how the timing and richness of linguistic environments affect the outcome achieved by the language-learner. The primary objective is to understand the abilities all human learners apply to language acquisition, and how those abilities change with age. The research focuses on a generation of deaf Nicaraguan children and adults whose initial language environment provided severely deficient linguistic input: it included no previously developed sign language. When first brought into a community in the late 1970s, they began to create a new sign language, that is, they acquired something not available in their language environment. The study of the mechanisms by which language is acquired is usually complicated by the fact that there are multiple possible sources for the information obtained; any innate features of language and contributions of previous generations will also be present in the typical language environment. In the case of Nicaraguan Sign Language, however, the roles of instinct and invention are enhanced relative to environmental input. The logic of this research is based on systematic comparisons between the language environment and the language outcome of each sequential cohort of language-learners to enter the community over a period of two decades. Because the language has increased in complexity over that time, today's adults represent the (severely impoverished) language input to the adolescents that followed them, who in turn represent the (richer) language input to today's children. Identifying the complexity added by each sequential cohort reveals the learners' contribution. A series of comparisons are therefore proposed, comparing the signed production and comprehension of signers who entered the community in different years. These explore basic word order, agreement markers, locative devices, incorporation of manner and path elements into the verb phrase, vocabulary innovation, and nominal classifiers. Together these comparisons will help reveal how human learners confronted with an impoverished language environment create, organize, and systematize language information, and how these abilities vary with age.